docs: def get_entities(self):
          """
          Fetch the entities extracted from this document by OpenCalais.
          """
          try:
              return self.__dict__['entities']
          except KeyError:
              entities = self._connection.fetch(
                  "documents/%s/entities.json" % self.id
              ).get("entities")
              obj_list = []
              for type, entity_list in list(entities.items()):
                  for entity in entity_list:
                      entity['type'] = type
                      obj = Entity(entity)
                      obj_list.append(obj)
              self.__dict__['entities'] = obj_list
              return self.__dict__['entities']